As global warming has recently been accelerated, glaciers and permanent snow maintaining more than 70% of fresh water existing on the earth are continuously melting.
If the glaciers and the permanent snow are melting, the fresh water is carried away and the sea level rises, thereby causing countries adjacent to the seashore to sink in seawater. In the long term, change in salinity of seawater may destroy the aquatic ecosystem of the sea.
To solve such a problem that the glaciers or the permanent snow are gradually melting due to global warming, climatic environments have to be fundamentally changed. However, time and efforts are too long and too much to change the fundamental climatic environments through human endeavor.
Recently, there has been proposed a method of protecting the glaciers and the permanent snow by lowering temperature in a predetermined area as sunlight exposed in the air is artificially blocked to control a large amount of sunlight beating down on a predetermined area.
Representatively, US patent publication No. 2009/0032214, titled “SYSTEM AND METHOD OF CONTROL OF THE TERRESTRIAL CLIMATE AND ITS PROTECTION AGAINST WARMING AND CLIMATIC CATASTROPHES CAUSED BY WARMING SUCH AS HURRICANES”, discloses a method of blocking sunlight in a predetermined area, in which an airplane generates exhaust gas such as volcanic ash to thereby make atmospheric environments such as mini nuclear winter.
Although such a sunlight blocking method is easily applied to a relatively large area, the exhaust gas may remain in the air and move to another area by a convection current, thereby causing serious air pollution. Further, in a predetermined area, this method is difficult to keep a sunlight blocking condition to last for a long time.
Also, US patent publication No. 2008/0030884, titled “DEVICE AND METHOD FOR AFFECTING LOCAL CLIMATIC PARAMETERS”, discloses a method of blocking sunlight in a predetermined area, in which an unmanned aerial vehicle equipped with a sunlight reflector is aviated.
However, such a sunlight blocking method may have problems that exhaust gas of the unmanned aerial vehicle influences atmospheric contamination and unstable atmosphere in the troposphere makes it difficult to position the unmanned aerial vehicle. Also, the unmanned aerial vehicle needs periodical refueling and maintenance, and is hard to stay for a long time in the troposphere.
Further, as shown in FIG. 1, the reflector installed in the unmanned aerial vehicle maintains level with a land surface in the troposphere, so that it is thus difficult to effectively block the sunlight beating down on the land surface at a predetermined angle. Therefore, the blocked area is not optimized.